Along with continuous improvement of technology, a user's requirement for a liquid crystal display device is increasing and a thin film transistor-liquid crystal display (TFT-LCD) has also become a popular display used in a product such as a mobile phone, a tablet computer, etc. Moreover, along with the popularity of the display device, a user's requirement for a large-size display device is increasingly common.
The performance of the TFT determines the display quality of LCD. Amorphous silicon is often used for an active layer in mass production, but amorphous silicon has many defects and the mobility of amorphous silicon is low. The actual mobility of carrier of the amorphous silicon TFT is about 10 cm2/(V*s). Due to too many defects, most of electric charges attracted by the gate electrode is grabbed by the defects and is unable to provide electrical conductivity. This will cause that the mobility of equivalent carriers merely remains 1 cm2/(V*s), which cannot meet the demand for large-size display devices.
To improve the mobility of the active layer, the metal oxide semiconductor is used to prepare the active layer in the prior art. Some metal oxide semiconductor has not the higher mobility. Some metal oxide semiconductor has the relatively higher mobility, but has the relatively larger leakage current. It will affect the performance of TFT and result in abnormal display of the display devices.